Jesus said that when we are faithful in little things it shows that we will be worthy of great things. Look at Luke 16:10:
He who is faithful in what is least is faithful also in much; and he who is unjust in what is least is unjust also in much.
David was amazing at great things, but slowly he began to change because of his rationalizing small little things. This study is about how deadly can be the results of rationalizing sin.
2 Samuel 11